Justification:
There are no published data about population trends or total numbers of mature animals for this species. There is very little available information about its extent of occurrence or its area of occupancy. There have been no quantitative analyses examining the probability of extinction of this species. As a result, the assessors have insufficient data to properly assess the species against any of the IUCN criteria. A Data Deficient (DD) listing is consistent with that recommended by an assessment conducted for Environment Australia (Pogonoski et al. 2002).

Hippocampus whitei was previously listed in 1996 as VU A2cd under the 1994 criteria. This assessment was based on suspected past declines in occupancy, occurrence and habitat, as well as on potential levels of exploitation. In reassessing the species under the new criteria and with greater taxonomic understanding we find that no appropriate data on biology and ecology, habitat, abundance or distribution are available for this species. Further research is needed. Assessed as Data Deficient under the new criteria.

Hippocampus whitei are found to depths of 25 m in shallow, weedy, inshore areas, in Zostera spp. seagrass beds, on sponges, and often under jetties on kelp holdfasts (Kuiter 1997). They are also found on manmade objects such as shark nets (A.C.J. Vincent, pers. obs.). Hippocampus whitei breed from October to April. Within this breeding season, they are site-faithful to a home range (averaging 8 m² for males, 12 m² for females: Vincent et al. in review) and are faithful to a single mate (Vincent and Sadler 1995).

This species may be particularly susceptible to decline. The limited information on habitat suggests they inhabit shallow sea-grass beds (Kuiter 1997) that are susceptible to human degradation, as well as making them susceptible to being caught as bycatch. All seahorse species have vital parental care, and many species studied to date have high site fidelity (Perante et al. 2002, Vincent et al. in review), highly structured social behaviour (Vincent and Sadler 1995), and relatively sparse distributions (Lourie et al. 1999). The importance of life history parameters in determining response to exploitation has been demonstrated for a number of species (Jennings et al. 1998).

Hippocampus whitei is caught for the aquarium trade, and mostly sold on the domestic market (Vincent 1996). The volume of this trade is unknown, but without appropriate management this trade might represent a threat to the species. Small numbers of H. whitei are probably also taken as bycatch in the southeast trawl fishery (Australian Fisheries Management Authority 1999).

The entire genus Hippocampus was listed in Appendix II of CITES in November 2002. Implementation of this listing will begin May 2004. The Australian populations of this species were moved under the Australian Wildlife Protection Act in 1998, so export permits are now required. The permits are only granted for approved management plans or captive bred animals. Such management was transferred under the new Environment Protection and Biodiversity Conservation Act in 2001. Many states also place their own controls on the capture and/or trade of syngnathid fishes. Further research on this species biology, ecology, habitat, abundance and distribution is needed.